Outline

Objective

To explore the visual perceptions evoked by acute electrical stimulation of the human retina with regard to the development of a chronic epiretinal implant.

Methods

A multicenter study with 20 subjects suffering from retinitis pigmentosa has been initiated considering strict inclusion and exclusion criteria. 15 subjects with visual acuities from 1/50 to no light perception and a mean age of 54 years underwent acute stimulation until abstract submission. Stimulation procedure is done during a pars plana vitrectomy with a maximum duration of 30 minutes. For stimulation a microcontact film with IrOx-electrodes connected by cable to a current generator is positioned epiretinally in the macular area. After repeated stimulation, the microcontact film is removed. Standardized interviews are performed 15 and 90 minutes after operation.

Results

14 of 15 subjects reported pleasant and not flashy perceptions of coloured objects ranging in size from a head of a match to a football as seen from a distance of one meter. Perceptual brightness was described as clearly visible, comparable to the light of a candle. Even a patient who has been blind since 25 years experienced relevant and reproducible percepts. Threshold charges needed to generate visual perceptions proved to be different between individual patients. Except for retinal detachment in one patient (reattached), no other side effects were observed during the 3-month follow-up.

Conclusions

Acute electrical stimulation of the human retina using microcontact films may create useful visual perceptions even in totally blind patients. It can be performed without damaging the macula. Results are encouraging with regard to the implantation of a chronic epiretinal implant.